The present invention relates to a catalytic converter for removing noxious elements from the exhaust gas stream of the internal combustion engine.
There have been provided three kinds of converters, namely a reducing catalytic converter for elimination of nitrogen oxides, an oxidizing catalytic converter for the elimination of carbon monoxide and hydrocarbons, and a three-way converter for reacting the three noxious elements at the same time. The converter comprises a catalyst bed comprising a pellet type catalyst element or monolithic or honeycomb catalyst element. The monolithic catalyst element has a series of longitudinally oriented passages each which substantially has a quadrilateral section having a side length of about 1 to 1.6 mm, so that the exhaust gases may flow smoothly through the catalyst element with small back pressure. However, there is a problem that the reaction may not be sufficiently carried out to reduce each noxious component to the required level because of a short residence time of the gas flow.